Logic 9 Logic 9 crashes when using Ez drummer

I have been using logic 9 for many years without problems. Since upgrading to Mavericks from Snow Leopard I have had repeated crashes when using EZ drummer. Very high cpu spikes and Logic stops. If I reboot Logic on most occasions things are back to normal but on other occasions I have to shut the Mac down completely and start again.
If I remove EzDrummer from the project I have no problems.
I use a Mac Pro 8 core 3.0ghz with 8 gig ram, running 64 bit mode, with separate internal drive for audio.
I am tempted to upgrade to Yosemite but my Tascam Dm4800 doesn't support it yet! Any suggestions would be most welcome